OBJECTIVE: To produce Toxocara canis infection of the primate eye and to study its onset, course and termination by clinical and histopathologic correlations. To evaluate the routes by which Toxocara canis reaches the eye and produces ocular infection and to correlate the type of infection produced with each route of entry. METHODS: Toxocara canis adult larvae are obtained from puppies. From these female worms eggs are harvested, pooled and incubated. After embryonation larvae are hatched from these eggs in vitro, suspended in saline and counted. Ocular toxocariasis is produced in primates by 6 routes in 2 sets of monkeys. Routes are: 1. Gastric tube administration of Toxocara eggs; 2. Unilateral intracarotid injection of freshly hatched larvae; 3. Retrobulbar injection of larvae suspension in various amounts and volumes; 4. Intravitreal injection of larvae suspension in various amounts and volumes; 5. Subarachnoid tissues of optic nerve; 6. Tear film. Groups are: A. Primates not previously exposed to Toxocara infection; B. Primates who have received Toxocara eggs orally 4 weeks prior to present exposure. The eyes of primates so exposed are evaluated by periodic ocular examination by slit-lamp biomicroscopy, indirect ophthalmoscopy and contact lens slit-lamp biomicroscopy. The ocular lesions are photographed and the eyes are removed and studied histologically at appropriate intervals.